Re: gnuplot on 64-bit Windows

[Bastian M. <bma...@we...>]

Am 25.07.2013 10:41, schrieb Allin Cottrell:
> On Wed, 24 Jul 2013, sfeam (Ethan Merritt) wrote:
>
>> On Wednesday, 24 July 2013, Allin Cottrell wrote:
>>> On Wed, 24 Jul 2013, sfeam (Ethan Merritt) wrote:
>>>
>>>> On Wednesday, 24 July 2013, Allin Cottrell wrote:
>>>>> I have need of a 64-bit Windows build of gnuplot and I've been
>>>>> working on cross-compiling from Linux using mingw64. I see
>>>>> several places in current CVS where the code generates errors
>>>>> and warnings. I'm attaching a patch-set which quells the
>>>>> errors and warnings, but unfortunately I'm not able to test on
>>>>> win64 at present.
>>>>
>>>> I can't help with evaluation of the full patch, but one set of
>>>> changes strikes me as being wrong on the face of it:
>>>>
>>>> %%%%%%%%%%%%%%
>>>> +#ifdef _WIN64
>>>> +INT_PTR CALLBACK PrintDlgProc(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam);
>>>> +#else
>>>> BOOL CALLBACK PrintDlgProc(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam);
>>>> +#endif
>>>> %%%%%%%%%%%%%%
>>>>
>>>> There's no way it can be correct to label a Boolean value  as a pointer.
>>>>

This is an (understandable) misunderstanding. INT_PTR is not a pointer 
type, but an integer large enough to do pointer calculations with. See e.g.
http://msdn.microsoft.com/en-us/library/windows/desktop/aa383751%28v=vs.85%29.aspx
Thus, the changes are indeed correct and is now included in CVS.

   Bastian


>>>> The equivalent substitution occurs several places in your patch.
>>>> I didn't check each one, but the routine PrintDlgProc really does return
>>>> TRUE or FALSE, so I think at least in this case, if not all of them,
>>>> the original code was correct.
>>>
>>> It's strange, I agree, but the original code throws a warning.
>>> The caller, in all cases, is CreateDialogParam() and the
>>> callback is the fourth argument, of type DLGPROC, in relation
>>> to which the msdn doc points us to "DialogProc callback
>>> function"
>>>
>>> http://msdn.microsoft.com/en-us/library/windows/desktop/ms645469%28v=vs.85%29.aspx
>>>
>>> where we find:
>>>
>>> <quote>
>>> Return value
>>>
>>> Type: INT_PTR
>>>
>>> Typically, the dialog box procedure should return TRUE if it
>>> processed the message, and FALSE if it did not. If the dialog
>>> box procedure returns FALSE, the dialog manager performs the
>>> default dialog operation in response to the message.
>>> </quote>
>>
>> [shudder]
>
> Yes, indeed.
>
>> Nevertheless, wouldn't your change just shift the site of the
>> error/warning message?  Now the prototype says it returns
>> INT_PTR but the function itself still says it returns BOOL.
>> So there is still a mismatch in types.
>
> My patches also change the return type of the relevant
> callback functions to INT_PTR for win64. However, given how
> broken the MS design is, I'd be happy to leave things as they
> were (in respect of CreateDialogParam) and put up with the
> warnings from gcc. If it might be useful I can submit an
> alternative version of the patch-set.
>
> Allin Cottrell